Conventionally, ropes are made out of coconut fibre and other natural materials. Such ropes are widely used in seaweed cultivation, but in general, the durability of the ropes is low in seawater. Ropes are also available which are made up of synthetic/semi-synthetic fibres such as nylon, polyester, etc. Such ropes are routinely used in seaweed cultivation but their low/poor biodegradability is a great concern.
Reference may be made to the publication of Ghosh et al. (Polymer International, 53, 339-343; 2004) wherein it has been stated that grafting of vinyl acetate onto the low density polyethylene (LDPE)-starch blend films makes them suitable for printing and packaging applications. They used commercially available blend films made of synthetic polymer and starch under inert atmosphere using hazardous chemicals (e.g. HNO3) during process, and used for printing and packaging applications. It is pertinent to mention here that the said reference does not mention the use of seaweed phycocolloids for making biodegradable hydrophobic composites for aqueous applications including seaweed cultivation.
Reference may be made to U.S. Pat. No. 6,294,202B1, wherein disclosed is a process for making water-insoluble biodegradable composition containing polyanionic polysaccharides and hydrophobic bioabsorbable polymers to prepare film, foam, mesh matte, or to cast on top of any surface. It is pertinent to mention here that the said reference reports the formation of compositions containing polyanionic polysaccharides and hydrophobic bioabsorbable polymers or copolymers. However, there is no report on the formation of biodegradable hydrophobic composites based on seaweed polysaccharides for novel applications including seaweed cultivation in sea water.
Reference may be made to US20040171545A1, wherein synthetic protein copolymers with plastic and elastic properties, and methods producing the copolymers, are disclosed. The process producing synthetic protein copolymer comprising at least one hydrophilic block and at least one hydrophobic block. It is pertinent to mention here that the said reference reports the formation of synthetic protein copolymers with plastic and elastic properties and does not describe any composition or process for the preparation of biodegradable hydrophobic composites based on seaweed phycocolloids for potential applications including seaweed cultivation.
Reference may be made to US20050161857A1, wherein recited is a method of producing a polymeric fibre (poly caprolactone) comprising: dissolving at least one fibre forming polymer in a solvent so as to form a polymer solution, and feeding the polymer solution under gravity through an orifice directly into a non-solvent to cause formation of a polymeric fibre in the non-solvent. It is pertinent to mention here that the said reference reports the formation of polymeric fibres from the synthetic polymer (e.g. poly-caprolactone) and does not describe any composition or process for the preparation of biodegradable hydrophobic composites based on seaweed phycocolloids.
Reference may be made to US20030118692A1, wherein reported is a method for the preparation of biodegradable elastomeric material from glycerol and diacid like malonic acid, succinic acid, adipic acid, glutaric acid, pimelic acid etc. to prepare different shapes of particles, tubes, spheare, strand, coiled strands capillary network, film, fibers, mesh and sheet. It is pertinent to mention here that the said reference reports the formation of biodegradable elastomeric materials using glycerol and diacids and does not describe any composition or process for the preparation of biodegradable hydrophobic composites based on seaweed phycocolloids for novel applications including seaweed cultivations in sea water.
Reference may be made to JP2000-093080, wherein disclosed is the use of polysaccharides like polyvinyl alcohol, polyvinyl pyrrolidone, sodium alginate, etc. in preparation of antibacterial and antifungal agent composition, which is soluble when used. It is pertinent to mention here that the said reference reports the formation of soluble materials and does not describe any composition or process for the preparation of biodegradable hydrophobic composites which are insoluble in water.
Reference may be made to Polymer International. 2001 50: 1103-1108, wherein use of poly(vinyl alcohol) and K-carrageenan in preparation of films based on poly(vinyl alcohol)/K-carrageenan blends and their gelling properties is reported. However, there is no report on the formation of hydrophobic materials including ropes and other materials in this article.
Reference may be made to WO 2006059180 A3, wherein use of inexpensive semi-refined kappa carrageenan as a seaweed polysaccharide in preparation of tough, biodegradable films with improved performance over films obtained from refined kappa carrageenan is disclosed. However, these films are highly moisture sensitive and readily soluble in water and thus cannot be applied in activities such as seaweed cultivation in open sea water environment.
In short, it may be summarized that the hitherto reported prior art shows that the polymeric composites prepared from purely petrochemical substances or entirely natural substance have some inherent drawbacks. Totally synthetic polymeric materials have problems of degradation, while natural polymeric materials are highly moisture sensitive and not suitable for aqueous applications owing to their solubility. For instance, seaweed derived phycocolloids such as agar, carrageenans, agarose, alginate are excellent gel formers and used as thickeners, but are highly moisture sensitive. Further, due to their high solubility in water and hydrophilic nature, these can be used only for the formation of films and are not good for aqueous applications because the hitherto reported composites made from them readily solubilise in water. In order to be eco-friendly as well as suitable for applications in water the composites must be hydrophobic.
Therefore, the inventors of the present invention realized that there exists a dire need to solve the issues discussed above and provide a composite through copolymerisation technique, to obtain controlled/completely hydrophobic biodegradable materials. It is evident from the prior art that there are no examples wherein polymers derived from seaweeds are utilised for preparation of hydrophobic composite materials which can be used for varied aqueous applications including seaweed cultivation in the sea water conditions.